Skip to main content

DEVELOPMENT OF MAGNESIUM ALLOYS FOR PRESSURE DIE CASTING IN THE SEMI SOLID STATE (RHEOCASTING AND THIXOCASTING)

Objective

These are to develop strong magnesium alloys whic h can be shaped in a semi-solid thixotropic state,e.g. by casting under pressure to form accurate pore-free components of good surface finish which can be strengthened by heat treatment. The effect of this on their susceptibility to electrochemical corrosion and an assessment of means of protecting them will be studied. C.E.M.E.F. are developing the Gircast process to produce AZ91 (Mg-Al-Zn) ingots suitable for semi- solid injection into a die. Fulmer is evaluating a wider range of alloy compositions for semi-solid processing and studying their casting and reheating behaviour. Both C.E.M.E.F. and Fulmer are preparing feedstock for S.A.M. to establish the industrial parameters for making components in a modified die-casting machine. Trento is developing electrochemical techniques capable of distinguishing the corrosion behaviour of the alloys in different stages of manufacture.
The objective of this work is to develop strong magnesium alloys which can be shaped in a semisolid state for example, by casting under pressure to form accurate pore free components of good surface finish which can be strengthened by heat treatment. The effect of this on their susceptibility to electrochemical corrosion and an assessment of means of protecting them will be studied. CEMEF are developing the Gircast process to produce AZ91 magnesium aluminium zinc ingots suitable for semisolid injection into a die. BNF Fulmer is evaluating a wider range of alloy compositions for semisolid processing and studying their casting and reheating behaviour. Both CEMEF and Fulmer are preparing feedstock for the Societe Aveyronnaise de Metallurgie (SAM) to establish the industrial parameters for making components in a modified die casting machine. The University of Trento is developing electrochemical techniques capable of distinguishing the corrosion behaviour of the alloys in different stages of manufacture.

Using the Gircast II process, CEMEF have established the parameters for preparing AZ91 ingots suitable for pressure die casting. BNF-Fulmer have also prepared a range of alloys with a suitable microstructure and cast ingots for shaping. SAM have developed an induction heating apparatus and carried out an extensive range of pressure die casting trials on both sets of alloys.

It has been shown that pressure die casting in the semisolid state reduces the shrinkage porosity, especially in thick sections and also improves the fatigue resistance of such alloys.

Electrochemical techniques have been developed by Trento and specimens from the various alloys at different stages in their processing have been tested. The results have shown that no substantial differences in performance can be expected from the various alloy additions made to improve the handlability of such alloys in the semisolid state.
- ARMINES WILL STUDY THE PREPARATION AND CASTING OF SEMI-SOLID MG ALLOYS (MG-AL-ZI OR MG-AL-SI).
-FULMER WILL STUDY PREPARATION OF FEEDSTOCK FOR THE INDIRECT ROUTE (THIXOCASTING) AND CHARACTERIZE ITS REHEATING AND DIE-CASTING BEHAVIOUR.
- S.A.M. WILL MANUFACTURE DIE-CASTING DIES AND CARRY OUT INDUSTRIAL EVALUATION OF SEMI-SOLID CASTING OF MG ALLOYS PREPARED BY FULMER AND ARMINES.
- UNIVERSITY OF TRENTO WILL CARRY OUT STUDIES OF ELECTROCHEMICAL AND CORROSION BEHAVIOUR OF MG ALLOYS AND DETERMINE THE NEED FOR PROTECTIVE COATINGS.

THE RHEOCASTING OR THIXOCASTING OF MAGNESIUM ALLOYS, WITH 20 TO 40 % LIQUID FOR INJECTING INTO A STEEL DIE BY PRESSURE, IS SUITED TO THE MASS PRODUCTION OF ACCURATE COMPONENTS FOR THE ROAD AND RAIL TRANSPORT, DOMESTIC, OFFICE AND ELECTRONIC EQUIPMENT SECTORS OF INDUSTRY.

THE ECONOMIC VALUE OF THE SEMI-SOLID PROCESS IS THAT THEY ENABLE SHAPES TO BE MADE BY PRESSURE DIE CASTING WHICH ARE NOT POSSIBLE BY LIQUID CASTING. THIS ENABLES FORGINGS AND ASSEMBLED ITEMS TO BE REPLACED BY DIRECTLY CAST COMPONENTS AT 30-60 % OF THE COST OF COMPETITIVE PROCESSES. BECAUSE OF THE REDUCTION IN THE TEMPERATURE OF PROCESSING AND THE NUMBER OF OPERATIONS, IT IS POSSIBLE TO SAVE 30% OF ENERGY IN PRODUCING THE CASTING.

THE MARKET FOR COMPONENTS MADE BY THESE PROCESSES WILL BE FOUND IN THE AEROSPACE AND VEHICLE INDUSTRIES WHERE REDUCTION IN WEIGHT IS OF CONSIDERABLE IMPORTANCE AND IN THE GENERAL AND DOMESTIC ENGINEERING INDUSTRIES WHERE THERE IS A NEED TO REDUCE THE WEIGHT OF RAPIDLY ACCELERATED AND DECELERATED COMPONENTS, E.G. IN COMPUTERS OPERATED PRINTERS.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Fulmer Research Laboratories Ltd
Address
Hollybush Hill Stoke Poges
SL2 4QD Slough
United Kingdom

Participants (3)

CEMEF (ARMINES)
France
SOCIETE AVEYRONNAISE DE METALLURGIE
France
UNIVERSITA' DEGLI STUDI DI TRENTO
Italy
Address

Trento